Radiation therapy is a common and effective approach for treating lung cancer, using high-energy beams to damage cancer cell DNA and inhibit tumor growth. The total number of treatments is not fixed, but is a carefully calculated plan based on the specific goal of the therapy and the nature of the disease. This division of the total radiation dose into multiple smaller treatments is known as fractionation. The schedule is highly individualized, ranging from a single session to more than 30 treatments, depending on the patient’s overall health, the tumor’s characteristics, and the intended outcome.
Factors Determining the Number of Treatments
The number of fractions is determined by several variables that influence the total dose required and how quickly it must be delivered. The primary factor is the intent of the treatment: curative, aiming to eliminate the cancer, or palliative, focusing on relieving symptoms. The stage and size of the lung tumor are also considerations, as smaller, localized tumors often require fewer, more concentrated treatments.
The tumor’s location plays a major role, especially if it is close to sensitive structures like the spinal cord, heart, or major airways. Treating near these organs necessitates smaller daily doses over a longer period to allow healthy tissue time to repair itself. The patient’s overall health status and ability to tolerate daily appointments also influence the decision between a long, standard course or a shorter, accelerated schedule. Concurrent chemotherapy alongside radiation may also change the fractionation plan to manage potential side effects.
Long-Course Radiation: The Conventional Curative Schedule
The conventional approach, often called long-course radiation or standard fractionation, is typically used for patients with locally advanced lung cancer (Stage II or Stage III) when the treatment goal is cure. This schedule involves delivering a relatively low dose of radiation each day, usually five times a week. A common protocol is a total of 60 to 66 Gray (Gy) delivered in 30 to 33 fractions.
This extended timeline of five to seven weeks is based on radiobiology. The low daily dose, typically 1.8 to 2.0 Gy per session, maximizes the chance of killing cancer cells while allowing healthy surrounding tissue time to repair damage. This repair mechanism is important for sensitive organs like the esophagus and spinal cord, which are often near the treatment area. The long-course schedule remains a standard for definitive treatment, often delivered concurrently with chemotherapy.
Short-Course Radiation: SBRT and Hypofractionation
Modern technology allows for highly accelerated schedules that significantly reduce the total number of required treatments. Stereotactic Body Radiation Therapy (SBRT), also known as Stereotactic Ablative Radiotherapy (SABR), delivers an extremely high dose of radiation precisely to a small, isolated target. This method is primarily reserved for early-stage lung cancers (typically Stage I) or for patients who are not candidates for surgery.
SBRT drastically compresses the treatment course, often requiring only one to five fractions in total. For example, a common schedule for a peripheral tumor might involve 50 to 60 Gy delivered in three to five sessions over one to two weeks. This high-dose approach is possible because advanced targeting technology spares healthy tissue, effectively ablating the tumor.
General hypofractionation is a slightly less intense, accelerated schedule used for some Stage II cases, typically involving 20 to 25 fractions. However, the number of SBRT fractions may be increased to 8 to 12 if the tumor is located centrally near sensitive structures like the main bronchus or esophagus, requiring greater caution.
Palliative Radiation Schedules
When the goal is symptom relief rather than cure, a significantly shorter course of radiation, known as palliative fractionation, is used. This therapy aims to quickly shrink the tumor to alleviate issues like pain, bleeding, or difficulty breathing, improving the patient’s quality of life. The total dose is lower than curative treatments because the focus is on rapid symptom control.
Palliative schedules are often the shortest, sometimes involving a single high-dose session. More commonly, a short course of five to ten treatments is delivered over one to two weeks. For example, 20 Gy in five fractions or 30 Gy in ten fractions are typical schedules used for prompt symptom relief. Shorter courses are preferred for patients with a limited prognosis to minimize time spent in treatment.